| Quote #4
"No, Kitty, you are mistaken. I do not love her, but I will avenge myself for her contempt."
Here D’Artagnan is trying to persuade himself and Kitty that he feels nothing for Milady, but rather that he is motivated to act in order to get revenge.
| Quote #5
"No, I do not hesitate; God forbid! But would it be just to allow me to go to a possible death without having given me at least something more than hope?"
First of all, D’Artagnan is basically asking for sex. Milady tells him yes, he can have that. She clearly has no qualms using sex in order to achieve her goal of revenge against the Comte de Wardes.
| Quote #6
D’Artagnan, on his part, had gained the summit of all his wishes. It was no longer a rival who was beloved; it was himself who was apparently beloved. A secret voice whispered to him, at the bottom of his heart, that he was but an instrument of vengeance, that he was only caressed till he had given death; but pride, but self-love, but madness silenced this voice and stifled its murmurs. And then our Gascon, with that large quantity of conceit which we know he possessed, compared himself with De Wardes, and asked himself why, after all, he should not be beloved for himself? (37.8)
D’Artagnan is perfectly aware that Milady is manipulating him in order to achieve of her goal of avenging herself on the Comte de Wardes, but he cannot help but feel persuaded that she really does love him.